1. Field of the Invention
This invention is related to a connector for coaxial lines. In particular, this invention is related to a connector which provides repeatable and secure contact between coaxial lines without utilizing a slotted female conductor.
2. Related Art
Coaxial line connectors are widely used to interface electrical systems. Such connectors must make durable mechanical contacts that are repeatable, provide good electrical performance and are easy to fabricate.
In a coaxial line a current is carried through both an inner conductor and an outer conductor. Generally, the inner conductor has a greater current density. The connector provides contact between the coaxial inner conductors and outer conductors that correspond to those of the two coaxial lines. However, the connector portion providing contact between the inner conductors of two coaxial lines is more critical than the connector portion providing contact between the outer conductors because of the differences in current density between the inner and outer conductors of the lines. It is therefore desirable to provide a secure connection between the two inner conductors of two coaxial lines.
In one known connector configuration, a coaxial connector has a female inner conductor connected to an end of the inner conductor of a first coaxial line and a male inner conductor connected to the end of the inner conductor of a second coaxial line whereby the male and female inner conductors are joined to form the connection between the inner conductors of the first and second coaxial line. A typical structure of such a male/female conductor configuration is illustrated in FIG. 1.
In FIG. 1 a female conductor 10 is connected to an inner conductor 12 of a first coaxial cable. The female conductor has at least one slot 13. A second inner conductor 16 associated with the second coaxial cable has a male conductor 14 connected to the inner conductor. As male conductor 14 is inserted into female conductor 10 the slot 13 provides the capability for allowing the female conductor to be flexible enough to receive the male conductor 14. In order to provide a secure contact, the known configuration utilizes a female conductor that has two or four slots. The slots provide an elastic or pliable characteristic to the female conductor so that the conductor makes good contact with the male conductor upon receiving the male conductor pin.
The electrical performance of such a connector as illustrated in FIG. 1 is degraded by the slots, especially at high frequency. The reason for this performance degradation is that the slots are exposed in radio frequency ("RF") fields and generate undesirable modes such as TE.sub.n1 for two slots or TE.sub.n2 for four slots. These undesirable high modes act like parasites to the operating TEM mode causing frequency sensitive reflections and high VSWR.
A solution to the problem caused by the slots has been proposed. Such a solution has been referred to as a "slotless contact". The structure of this contact is illustrated in FIG. 2. In this figure the inner conductor connector is a three-layer structure. A male conductor 22 of the inner conductor 26 of a first coaxial cable is captured by a female conductor 20 which has at least one slot. This configuration, however, includes a construction which prevents the slot or slots from being exposed in RF fields. In order to do this, a hollow cylindrical inner conductor member 24 is provided as a shielding or a shelter for the female conductor. Therefore, the term "slotless contact" is a misnomer as the female conductor still has slots, the difference is that the slots are shielded from the RF field so that degradation caused by the slots is reduced and the electrical performance is enhanced. However, there is a disadvantage associated with this approach. It involves a complex three layer structure which is difficult to fabricate and to assemble. It is difficult to construct such a three layer connector for use in a very high frequency environment, for instance a connector operable over a range of from DC to 100 GHZ, because the outer diameter of the inner conductor for such an operating range can only be about 0.5 millimeters. It is virtually impossible to make the inner conductor of such a size in a three-layer structure. Another problem with this structure is that there is a distance between the mechanical contacts at the tip of the ends of the female conductor which receive the male conductor and the electrical interface of the two coaxial inner conductors where the gap is caused by the configuration of the shielding conductor 24. Undesirable resonance will occur at certain frequencies thereby further degrading the performance of the connector.
Another known connector utilizes a non-mating connector shown in FIG. 7. Non-mating contacts 71 are disposed within hollow cylinders 72. The contact between cylindrical contact 72 and an inserted contact 71 is a regular sliding contact which has small gaps between the cylindrical and inserted contacts. Springs 73 provide the necessary force for bringing the sliding contact 71 of the respective coaxial lines together.